Electrolysis electrode and electrolyzer

ABSTRACT

To provide an electrolysis electrode having a more preferable shape in electrolyzing pure water, an alkali aqueous solution, or an aqueous solution of an alkali metal chloride at a lower voltage than ever before, and an electrolyzer using the same. An electrolysis electrode or the like including: a metal perforated plate having a value of Factor V of 40 or more represented by the formula: Factor V=Rs×Rc×F/100000, in which Rs is a planar direction surface area per unit area 1 dm 2  [cm 2 /dm 2 ], Rc is a thickness direction surface area per unit area 1 dm 2  [cm 2 /dm 2 ], and F is the number of mesh apertures per unit area 1 dm 2  (fine degree) [number/dm 2 ].

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Entry of International Patent Application Serial Number PCT/JP2020/023244, filed Jun. 12, 2020, which claims priority to Japanese Patent Application No. JP 2019-113078, filed Jun. 18, 2019, the entire contents of both of which are incorporated herein by reference.

FIELD

The present disclosure generally relates to electrolysis, including electrolysis electrodes, electrolyzers that use electrolysis electrodes, electrolysis electrodes in electrolyzers that use a diaphragm, and diaphragm electrolyzers.

BACKGROUND

In the case of obtaining hydrogen, oxygen, or chlorine gas, and an alkaline raw material such as caustic soda by electrolysis such as water electrolysis, alkaline water electrolysis, or brine electrolysis, the electric power consumption rate is reflected in the cost of producing products such as hydrogen gas, oxygen gas, caustic soda (NaOH), and chlorine gas (Cl2). Moreover, since electricity is used in electrolysis, it releases carbon dioxide (CO2) gas during the generation of electricity and thus has a negative impact on global warming. In such social settings, in operating an electrolyzer having a diaphragm or an ion exchange membrane electrolyzer, there currently is a need for an electrolyzer that can further reduce an electrolysis voltage.

For such a problem, various items such as the shape of a cathode, coating, and power feeding in an electrolyzer including a diaphragm or an ion exchange membrane have been researched so far. For example, Patent Document 1 discloses a technology to reduce an electrolysis voltage by making the shape of a mesh of an expanded metal used as a cathode smaller.

On the other hand, regarding an anode, Patent Document 2 discloses a technology to improve electrolysis performance by making the aperture ratio of a mesh of an expanded metal within a predetermined range. In addition, a technique to reduce an electrolysis voltage by applying a coating on an anode is known. Patent Document 3 discloses an anode composed of a metal mesh having substantially diamond-shaped perforations, in which the ratio of strand and perforation, and a long way distance LWD and a short way distance SWD of the perforations are set to be predetermined values. Patent Document 3 discloses that a platinum group metal oxide, magnetite, ferrite, cobalt spinel, or a mixed metal oxide can be used as a coating. Moreover, Patent Document 4 discloses an ion exchange membrane electrolysis anode which can electrolyze an aqueous solution of an alkali metal chloride at a lower voltage than ever before and can reduce the concentration of impurity gas contained in anode gas by making the thickness and the ratio of a short way SW to a long way LW, SW/LW, of the metal perforated plate within certain ranges. Furthermore, Patent Document 5 discloses an electrolysis electrode including a conductive base material made of a perforated metal plate and at least one catalyst layer formed on the surface of the conductive base material, in which the thickness of the electrolysis electrode is more than 0.5 mm and 1.2 mm or less, and a value C obtained by dividing the sum B of peripheral lengths of perforations of the electrolysis electrode by the aperture ratio A of the electrolysis electrode is more than 2 and 5 or less.

Various known prior art includes Patent JP 2012-140654 A (Patent Document 1), Patent JP 4453973 B2 (Patent Document 2), Patent JP S62-502820 A (Patent Document 3), Patent JP 6216806 B2 (Patent Document 4), Patent WO 2018/131519 (Patent Document 5).

From WO 2018/155503 A1 an electrolysis electrode is known. In order to obtain a water electrolysis device, which has low oxygen overvoltage, the surface of a nickel porous substrate of the electrode has a layer of metal oxide having a perovskite type structure. Further, U.S. Pat. No. 5,804,055 A describes another electrode for an electrochemical process with a flat plate core serving as a current distributor and multiple layers of a very thin, highly flexible metal mesh wound around the core.

SUMMARY

However, it was confirmed that the cell voltage becomes high or becomes low even when the shape of the electrolysis electrode described in the cited documents, in particular, the mesh shape satisfying the thickness and the ratio of the short way SW to the long way LW, SW/LW, of the metal perforated plate disclosed in Patent Document 4 is used.

Thus, an object of the present disclosure is to provide an electrolysis electrode having a more preferable shape in electrolyzing pure water, an alkali aqueous solution, or an aqueous solution of an alkali metal chloride at a lower voltage than ever before, and an electrolyzer using the same.

The present inventors conducted intensive research to solve the above-described problems, found that there is a correlation between an area Rs of plane axes (XY axes) per unit area 1 dm² (cm²/dm², hereinafter also abbreviated as plane axes area), an area Rc in a thickness direction (Z axis) per unit area 1 dm² (cm²/dm², hereinafter also abbreviated as thickness direction area), and a fine degree F. per unit area 1 dm² (hereinafter also abbreviated as fine degree), and a cell voltage, and further found that pure water, an alkali aqueous solution, or an aqueous solution of an alkali metal chloride can be electrolyzed at a lower voltage than ever before when an electrolysis electrode has a shape satisfying certain conditions of them to complete the present disclosure.

That is, an electrolysis electrode of the present disclosure including: a metal perforated plate having a value of Factor V of 40 or more represented by the following formula:

Factor V=Rs×Rc×F/100000,

-   -   in which Rs is a planar direction surface area per unit area 1         dm² [cm²/dm²], Rc is a thickness direction surface area per unit         area 1 dm² [cm²/dm²], and F is the number of mesh apertures per         unit area 1 dm² (fine degree) [number/dm²].

In the electrolysis electrode of the present disclosure, preferably, the value of Factor V is 70 or more. Moreover, the metal perforated plate is an expanded metal. Moreover, a ratio of a short way center-to-center distance SW to a long way center-to-center distance LW of a mesh of the expanded metal, SW/LW, is 0.45 or less, preferably, a short way center-to-center distance SW of a mesh of the expanded metal is 2.0 mm or less, and preferably, a thickness t of a mesh of the the expanded metal is 0.5 mm or less. Furthermore, preferably, a thickness t, a long way center-to-center distance, a short way center-to-center distance, and a strand of a mesh of the expanded metal are from 0.35 to 0.5 mm, from 2.9 to 3.2 mm, from 1.1 to 1.4 mm, and from 0.4 to 0.7 mm, respectively.

Furthermore, an electrolyzer of the present disclosure including: an anode; and a cathode, in which at least one of the anode and the cathode is the above-described electrolysis electrode of the present disclosure.

Preferably, the electrolyzer of the present disclosure includes a diaphragm for separating an anode chamber and a cathode chamber, preferably, the diaphragm is an ion exchange membrane or a porous membrane, and preferably, the diaphragm and the cathode or the anode are in contact.

There are advantageous effect of the present disclosure. For example, according to the present disclosure, an electrolysis electrode having a more preferable shape in electrolyzing pure water, an alkali aqueous solution, or an aqueous solution of an alkali metal chloride at a lower voltage than ever before, and an electrolyzer using the same can be provided.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic partial enlarged view of an electrolysis electrode according to one comparative example.

FIG. 2A is a schematic partial enlarged view of an electrolysis electrode according to one embodiment of the present disclosure.

FIG. 2B is a cross-sectional view along the line A-A of FIG. 2A.

FIG. 3A is a schematic partial enlarged view obtained by further enlarging a part of the schematic partial enlarged view illustrated in FIG. 2A.

FIG. 3B is a cross-sectional view along the line B-B of FIG. 3A.

FIG. 4 is a schematic cross-sectional view of an electrolyzer according to one embodiment of the present disclosure.

FIG. 5 is a graph illustrating a relationship between Factor V and a cell voltage reduction effect of the comparative Example 1.

FIG. 6 is a graph illustrating a relationship between Factor V and a cell voltage reduction effect of Example 2 according to the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents. Moreover, those having ordinary skill in the art will understand that reciting “a” element or “an” element in the appended claims does not restrict those claims to articles, apparatuses, systems, methods, or the like having only one of that element, even where other elements in the same claim or different claims are preceded by “at least one” or similar language. Similarly, it should be understood that the steps of any method claims need not necessarily be performed in the order in which they are recited, unless so required by the context of the claims. In addition, all references to one skilled in the art shall be understood to refer to one having ordinary skill in the art.

An electrolysis electrode of the present disclosure is an electrode used in an electrolyzer and, in particular, an ion exchange membrane electrolysis electrode used in an ion exchange membrane electrolyzer separated into an anode chamber housing an anode and a cathode chamber housing a cathode by an ion exchange membrane. In the present disclosure, the electrolysis electrode includes a metal perforated plate. FIG. 1 illustrates a schematic partial enlarged view of an electrolysis electrode according to one comparative example using a punching mesh in which diamond-shaped perforations are punched out. Moreover, FIG. 2A illustrates a schematic partial enlarged view of an electrolysis electrode according to a preferred embodiment of the present disclosure using an expanded metal, FIG. 2B illustrates a cross-sectional view along the line A-A of FIG. 2A, FIG. 3A illustrates a schematic partial enlarged view obtained by further enlarging a part of the schematic partial enlarged view illustrated in FIG. 2A, and FIG. 3B illustrates a cross-sectional view along the line B-B of FIG. 3A. In FIG. 1, FIG. 2A, FIG. 2B, FIG. 3A, and FIG. 3B, the punching mesh and the expanded metal are exemplified as a metal perforated plate 1. The metal perforated plate 1 may be a product obtained by laminating metal perforated plates.

As described above, a cell voltage has a correlation with an area Rs of plane axes (XY axes) per unit area 1 dm² (cm²/dm², hereinafter also abbreviated as plane axes area), an area Rc in a thickness direction (Z axis) per unit area 1 dm² (cm²/dm², hereinafter also abbreviated as thickness direction area), and a fine degree F. per unit area 1 dm² (hereinafter also abbreviated as fine degree), and the electrolysis electrode of the present disclosure is characterized by including a metal perforated plate having a value of Factor V of 40 or more represented by the following formula;

Factor V=Rs×Rc×F/100000.

A graph of Factor V and a cell voltage reduction effect has an approximate shape in either case of using the punching mesh or using the expanded metal and can be used regardless of the shape of the metal perforated plate 1. Moreover, since the expanded metal is characterized by including a step of notching and stretching a metal plate and performing rolling to flatten the surface, the cross-section is not perpendicular but inclined as illustrated in the cross-sectional view of FIG. 2B and the cross-sectional view of FIG. 3B, and an approximation formula indicated in Examples can be used in the calculation of Factor V, in particular, Rc.

In the case of using the punching mesh, a good cell voltage reduction effect can be obtained when Factor V is 70 or more, and in the case of using the expanded metal, a good cell voltage reduction effect can be obtained when Factor V is 40 or more. Although the reason why there is a difference in the value of Factor V by which a good cell voltage reduction effect can be obtained between the case of using the punching mesh and the case of using the expanded metal is not necessarily clear, as described below, the reason is assumed to be caused by resistance due to gas release or the like because the expanded metal is different from the punching mesh particularly in the shape in the thickness direction.

Moreover, in the case of using the expanded metal, even when Factor V is the same value, the cell voltage reduction effect becomes smaller in the case where a SW/LW ratio is more than 0.6 compared to the case where the SW/LW ratio is more than 0.45 and 0.60 or less. On the other hand, the case where the SW/LW ratio is 0.45 or less is preferable because the cell voltage reduction effect becomes larger compared to the case where Factor V is the same value and the SW/LW ratio is more than 0.45 and 0.60 or less. This is a phenomenon which is not found in the punching mesh, and when the expanded metal is used as the electrode shape, the ratio of SW and LW has a greater impact on the cell voltage reduction effect compared to the punching mesh. This is assumed to be caused by the impact of an angle in the thickness direction or the like on current distribution, resistance when generated gas is released from the electrode surface, and the like.

In the present disclosure, preferably, a short way center-to-center distance SW of a mesh of the expanded metal is 2.0 mm or less. By making the short way SW 2.0 mm or less, the current distribution during electrolysis can be more equalized.

Moreover, in the present disclosure, preferably, a thickness t of a mesh of the expanded metal is 0.5 mm or less. By making the thickness t of the mesh 0.5 mm or less, a mesh having smaller mesh apertures can be produced by an expanded metal cheaper than a punching mesh. It is known that, in the case of actually producing a mesh, producing of a mesh of the present disclosure, which has a thickness t of more than 0.5 mm, by an expanded metal is very difficult in a production process of the expanded metal.

In the electrolysis electrode according to the present disclosure, it is important only that the value of Factor V of the metal perforated plate 1 is 40 or more, and known configurations can be adopted for other configurations. For example, in the case of using an expanded metal as the metal perforated plate 1, a titanium expanded metal produced by shearing and then expanding a plate and flattened by rolling or the like can be preferably used. It is to be noted that a coating of an electrode catalyst material, such as a platinum group metal oxide, magnetite, ferrite, cobalt spinel, or a mixed metal oxide, may be formed on the surface of the electrolysis electrode to reduce an electrolysis voltage.

Moreover, as described above, in the electrolysis electrode of the present disclosure, laminated multiple layers of the metal perforated plates 1 may be used to ensure the strength. However, for example, in the case of being used as an electrode of an ion exchange membrane electrolyzer, the value of Factor V of the metal perforated plate 1 on the side in contact with an ion exchange membrane needs to be 40 or more

Next, an electrolyzer of the present disclosure will be described.

FIG. 4 is a cross-sectional view of an electrolyzer including a diaphragm according to one preferred embodiment of the electrolyzer of the present disclosure, and the electrolyzer of the present disclosure can be preferably used for not only ion exchange membrane electrolysis and brine electrolysis but also other electrolysis, water electrolysis, and alkaline water electrolysis. As illustrated in the drawing, a diaphragm electrolyzer 10 is separated into an anode chamber 12 and a cathode chamber 13 by a diaphragm 11, and an anode 14 and a cathode 15 are housed in the anode chamber 12 and the cathode chamber 13, respectively. In the example illustrated by the drawing, the anode 14 is fixed to an anode power feeder 16 like an anode rib in the anode chamber 12, and the cathode 15 is fixed to the cathode chamber 13 through a cathode current collector 17 in the cathode chamber 13. It is to be noted that, as one of more preferred embodiments of the present disclosure, the cathode current collector has elasticity, and a state where the anode 14, the diaphragm 11, and the cathode 15 are in close contact one another at a preferred pressure is maintained.

In the diaphragm electrolyzer 10, the above-described electrolysis electrode of the present disclosure is used for an electrode, in particular, the anode 14. As described above, by applying the electrolysis electrode of the present disclosure to the diaphragm electrolyzer 10, an electrolyte solution, for example, an aqueous solution of an alkali metal chloride or an aqueous solution can be electrolyzed at a lower voltage than ever before.

The diaphragm electrolyzer 10 is separated by the diaphragm 11 into the anode chamber 12 in which the anode 14 is housed and the cathode chamber 13 in which the cathode 15 is housed, it is important only that the above-described electrolysis electrode of the present disclosure is used for an electrode, in particular, the anode 14, and configurations of a known diaphragm electrolyzer can be adopted for other configurations.

For example, the cathode 15 is not particularly limited as long as it is a cathode usually used for electrolysis, and a known cathode can be used, for example, an expanded metal made of corrosion-resistant metal such as nickel can be used. It is to be noted that a coating of an electrode catalyst material containing a platinum group metal oxide may be formed on the surface of the cathode 15.

Moreover, in the example illustrated by the drawing, the anode chamber 12 and the cathode chamber 13 are hermetically laminated through a gasket 18, and the distance between the anode 14 and the cathode 15 is adjusted by the thickness of the gasket 18 and the lengths of the anode power feeder 16 and the cathode current collector 17. Regarding between the cathode 15 and the diaphragm 11, the electrolyzer may be operated with the diaphragm 11 and the cathode 15 substantially in close contact, or the electrolyzer may be operated with a gap of about 1-2 mm as illustrated in the drawing.

It is to be noted that, in the example illustrated by the drawing, a unit electrolyzer in which a pair of the anode chamber 12 and the cathode chamber 13 is laminated is shown, but the diaphragm electrolyzer 10 may be an electrolyzer in which a plurality of such unit electrolyzers are laminated. Moreover, the electrolyzer of the present disclosure may be an electrolyzer in which bipolar units, each of which has an anode and a cathode on both sides by connecting outer surfaces of an anode chamber and a cathode chamber to each other, are laminated with diaphragms sandwiched therebetween, and an anode chamber unit and a cathode chamber unit, one of which has an anode chamber or a cathode chamber, are laminated on both ends with the diaphragms sandwiched therebetween.

In order to perform brine electrolysis using the diaphragm electrolyzer 10 of the present disclosure, a current is made to flow between both electrodes while supplying a brine aqueous solution from an anode chamber inlet 12 a provided in the anode chamber 12 and a diluted aqueous solution of sodium hydroxide from a cathode chamber inlet 13 a provided in the cathode chamber 13. At that time, by making the pressure of the cathode chamber 13 higher than that of the anode chamber 12 to make the diaphragm 11 closely contact the anode 14, so that the diaphragm electrolyzer 10 can be efficiently operated. It is to be noted that an anode solution is discharged together with a product of the electrolysis from an anode chamber outlet 12 b in the anode chamber 12, and a cathode solution containing a product of the electrolysis is also discharged from a cathode chamber outlet 13 b in the cathode chamber 13. Moreover, an ion exchange membrane is used as a diaphragm in the case of performing brine electrolysis.

EXAMPLES

Hereinafter, the present disclosure will be described in more detail using Examples.

Example 1 (Comparative Example)

Samples 1 to 16 of electrolysis anodes formed from samples obtained by applying DSE coatings on titanium base materials for punching-type meshes were produced according to the conditions indicated in Table 1 below, and each of them was installed into an ion exchange membrane electrolyzer of a type illustrated in FIG. 4. Then, electrolysis of a brine solution was performed according to the electrolysis conditions described below. It is to be noted that the electrolysis area of the ion exchange membrane electrolyzer was 1 dm², a cation exchange membrane Flemion F-8080A manufactured by AGC Inc. was used for a diaphragm, and an active cathode using a fine mesh made of nickel as a cathode base material and subjected to a coating of NRG-V manufactured by De Nora Permelec Ltd was used. The fine mesh means an expanded metal having fine perforations or a plain-woven mesh. Moreover, in order to make a gap between the diaphragm and the electrodes zero, brine electrolysis was performed using an elastic body as a structure for feeding power to the cathode in a cell having a structure in which the diaphragm is pressed and further the cathode is pressed to the anode.

It is to be noted that LW, SW, ST, t, S, F, Rs, and Rc in Table 1 are as follows (regarding LW, SW, and ST, also refer to the description in FIG. 1):

LW: long way center-to-center distance, mm, SW: short way center-to-center distance, mm, ST: strand (perpendicular mesh width), mm, t: mesh thickness, mm, S: mesh aperture ratio, %, calculated by the following calculation:

${S = \frac{\left\{ {\left( \frac{LW}{2} \right) - \sqrt{\left( \frac{ST}{2} \right)^{2} + \left( {ST} \right)^{2}}} \right\}*\left\{ {\left( \frac{SW}{2} \right) - \sqrt{\left( \frac{ST}{2} \right)^{2} + \left( \frac{ST}{4} \right)^{2}}} \right\}*4}{LW*SW}},$

F: fine degree per unit area 1 dm², calculated by the following formula, hereinafter also abbreviated as fine degree:

F=(100/LW)×(100/SW),

Rs: area of plane axes (XY axes) per unit area 1 dm², cm²/dm², calculated by the following formula, hereinafter also abbreviated as plane axes area:

Rs=(100−S)×100, and

Rc: area in thickness direction (Z axis) per unit area 1 dm², cm²/dm², hereinafter also abbreviated as thickness direction area, Rc=(region 2 indicated by dashed line in FIG. 1, i.e., mesh total peripheral length per one mesh)×F×t, specifically, calculated by the following formula:

Rc= $\left\lbrack {\left\{ {\left( \frac{LW}{2} \right) - \sqrt{\begin{matrix} {{\left( \frac{ST}{2} \right)^{2}*\left( \frac{LW}{SW} \right)^{2}} +} \\ \left( \frac{ST}{2} \right)^{2} \end{matrix}}} \right\}^{2} + \left\{ {\left( \frac{SW}{2} \right) - \sqrt{\begin{matrix} {{\left( \frac{ST}{2} \right)^{2}*\left( \frac{SW}{LW} \right)^{2}} +} \\ \left( \frac{ST}{2} \right)^{2} \end{matrix}}} \right\}^{2}} \right\rbrack^{0.5} \star {8t} \star {{\frac{F}{100}\left\lbrack {{cm}2/{dm}2} \right\rbrack}.}$

Electrolysis Conditions

An aqueous solution of 200±10 g/L NaCl was used as an anode solution, and an aqueous solution of 32±0.5% by mass of NaOH was used as a cathode solution. The electrolysis temperature was from 86 to 88° C., and the current density was 6 kA/m².

Evaluation

The operation was continuously performed until the cell voltage was stabilized (for about from 20 to 30 days), and an evaluation was performed by the cell voltage after being stabilized. A result of the cell voltages when the conditions of various meshes were changed is shown in Table 1. It is to be noted that all these cell voltages were compared by values corrected to conditions of 90° C. and 32.0% by mass of NaOH. As the cell voltage reduction effect, a value of Sample-1 was standardized, and a larger value indicates a larger reduction effect.

TABLE 1 Long Way Short Way Center-to- Center-to- Strand Mesh Thickness Center Center (Perpendicular Mesh Aperture Plane Axes Direction Fine Cell Voltage Distance Distance Mesh Width) Thickness Ratio S Area Rs Area Rc Degree F Factor Reduction LW [mm] SW [mm] ST [mm] t [mm] [%] [cm²/dm²] [cm²/dm²] [pc/dm²] V Effect [mV] Sample-1 4.00 2.00 0.2 0.3 78.9% 21.1 59.6 1250 16 0 Sample-2 4.00 2.00 0.6 0.3 44.2% 55.8 44.6 1250 31 30 Sample-3 4.00 2.00 0.2 0.5 78.9% 21.1 99.3 1250 26 11 Sample-4 4.00 2.00 0.6 0.5 44.2% 55.8 74.3 1250 52 37 Sample-5 3.00 1.50 0.2 0.3 72.4% 27.6 76.1 2222 47 47 Sample-6 3.00 1.50 0.4 0.3 49.3% 50.7 62.8 2222 71 56 Sample-7 3.00 1.50 0.2 0.5 72.4% 27.6 126.8 2222 78 50 Sample-8 3.00 1.50 0.4 0.5 49.3% 50.7 104.6 2222 118 54 Sample-9 2.00 1.00 0.2 0.3 60.3% 39.7 104.2 5000 207 63 Sample-10 2.00 1.00 0.3 0.3 44.2% 55.8 89.2 5000 249 67 Sample-11 2.00 1.00 0.2 0.5 60.3% 39.7 173.6 5000 345 64 Sample-12 2.00 1.00 0.3 0.5 44.2% 55.8 148.6 5000 415 73 Sample-13 3.00 1.20 0.4 0.5 44.0% 56.0 115.1 2778 179 60 Sample-14 3.00 1.20 0.4 0.3 44.0% 56.0 69.0 2778 107 41 Sample-15 2.50 1.10 0.3 0.5 50.9% 49.1 139.5 3636 249 65 Sample-16 2.50 1.10 0.3 0.3 50.9% 49.1 83.7 3636 150 53

Table 1 indicates the following.

In a comparison of Sample-1 with Sample-2, in Sample-2 having the same LW, SW, and t, and the plane axes area Rs increased by 2.6 times compared to Sample-1 by changing ST, the cell voltage was decreased by 30 mV.

Moreover, in a comparison of Sample-1 with Sample-3, in Sample-3 having the same LW, SW, and ST, and the thickness direction area Rc increased by 1.67 times compared to Sample-1 by increasing t by 1.67 times, the cell voltage was decreased by 11 mV.

Furthermore, in a comparison of Sample-1 with Sample-4, in Sample-4 having the plane axes area Rs increased by 2.6 times compared to Sample-1 and the thickness direction area Rc increased by 1.25 times compared to Sample-1, the cell voltage was decreased by 37 mV.

Next, in a comparison of Sample-1 with Sample-5, in Sample-5 having the plane axes area Rs increased by 1.3 times compared to Sample-1, the thickness direction area Rc increased by 1.28 times compared to Sample-1, and the fine degree increased by 1.78 times compared to Sample-1 by decreasing LW and SW while remaining the same ratio of SW and LW and keeping the values of ST and t the same, the cell voltage was decreased by 47 mV.

Moreover, in Sample-9 having the plane axes area Rs increased by 1.9 times compared to Sample-1, the thickness direction area Rc increased by 1.7 times compared to Sample-1, and the fine degree increased by 4.0 times compared to Sample-1 by further decreasing LW and SW while remaining the same ratio of SW and LW and keeping the values of ST and t the same, the cell voltage was decreased by 63 mV.

Furthermore, Sample-12 to Sample-16 were performed with SW/LW changed to 0.4, which is 0.5 in Sample-1 to Sample-12. This is a condition where the fine degree becomes larger, and as a result, in Sample-13, the cell voltage was decreased by 6 mV compared to Sample-8.

According to the above result, after conducting intensive research, it was found that the cell voltage has a correlation with Factor V represented by the following formula, which is represented by a multiplication of Rs, Rc, and F of the mesh:

Factor V=Rs×RC×F/100000.

A correlation of Factor V with the cell voltage of Table 1 is illustrated in FIG. 5. It is found from FIG. 5 that the cell voltage reduction effect changes significantly at the value of Factor V around 60 and a good cell voltage reduction effect can be obtained when the value of Factor V is 70 or more.

Example 2 (According to the Present Disclosure)

In the following Samples 17 to 38 shown in Table 2 are discussed. Only Samples 32, 34, 37 and 38 are examples according to the invention. The other samples are shown as comparative examples, only.

Samples 17 to 38 of electrolysis anodes formed from samples obtained by applying DSE coatings on titanium base materials for expanded metals, in which factors of shape research become complex, were produced according to the conditions indicated in Table 2 below, and each of them was installed into an ion exchange membrane electrolyzer of a type illustrated in FIG. 4. Then, electrolysis of a brine solution was performed according to the electrolysis conditions described below. It is to be noted that, similarly to Example 1, the electrolysis area of the ion exchange membrane electrolyzer was 1 dm2, a cation exchange membrane Flemion (a registered trademark) F-8080A manufactured by AGC Inc. was used for a diaphragm, and an active cathode using a fine mesh made of nickel as a cathode base material and subjected to a coating of NRG (a registered trademark)-V manufactured by De Nora Permelec Ltd was used.

LW, SW, ST, t, S, F, Rs, and Rc in Table 2 are the same as those in Table 1, and basically have the same calculation formulas as in the punching mesh. However, actually, since the expanded metal is characterized by including a step of notching and stretching a metal plate and performing rolling to flatten the surface, the cross-section is not perpendicular but inclined as illustrated in FIG. 2B.

Thus, in the expanded metal, since there is an area indicated by a hatched part in FIG. 2A and FIG. 3A, the actual mesh aperture ratio S tends to become smaller than the calculation result of the formula regarding the mesh aperture ratio S indicated in Example 1. Thus, a projected area when being exposed to light from the surface, i.e., an area A of a white part in FIG. 2A and FIG. 3A was measured by a microscope as an actual perforation area, and the mesh aperture ratio S was calculated based on the area A. Moreover, Rs was calculated using an area of a gray part excluding the hatched part and the white part as the plane axes area. It is to be noted that the hatched part indicates a state where an area in the thickness direction is viewed.

Since it is difficult to observe the actual thickness, the thickness direction area Rc was simply calculated from the following formula.

The long way center-to-center distance LW was also measured together with the area A by the microscope, the short way center-to-center distance SW was calculated from the area A and LW by approximating the perforation shape by a diamond shape, and the region 2 indicated by the dashed line in FIG. 2A, i.e., the mesh total peripheral length W per one mesh was calculated from the values of the area A, LW, and SW by the following formula based on the diamond shape approximation of the perforation shape.

The thickness direction area Rc was determined using W, L1 and L2 illustrated in FIG. 3A, and the mesh thickness t by triangle approximation of the width in the thickness direction, which is indicated in the following formulae:

${W = {8*\left\{ {\left( {\frac{A}{2}*\frac{LW}{SW}} \right) + \sqrt{\left( \frac{SW}{LW} \right)^{2}*\left( {\frac{A}{2}*\frac{SW}{LW}} \right)}} \right\}}},{and}$ ${Rc} = {\frac{W}{2}*\left( {\sqrt{\left( {L1} \right)^{2} + t^{2}} + \sqrt{\left( {L2} \right)^{2} + t^{2}}} \right)*{\frac{F}{100}.}}$

Electrolysis Conditions

Similarly to Example 1, an aqueous solution of 200±10 g/L NaCl was used as an anode solution, and an aqueous solution of 32±0.5% by mass of NaOH was used as a cathode solution. The electrolysis temperature was from 86 to 88° C., and the current density was 6 kA/m2.

Evaluation

Similarly to Example 1, the operation was continuously performed until the cell voltage was stabilized (for about from 20 to 30 days), and an evaluation was performed by the cell voltage after being stabilized. A result of the cell voltages when the conditions of various meshes were changed is shown in Table 2. It is to be noted that all these cell voltages were compared by values corrected to conditions of 90° C. and 32.0% by mass of NaOH. As the cell voltage reduction effect, a value of Sample-17 was standardized, and a larger value indicates a larger reduction effect.

TABLE 2 Long Way Short Way Center-to- Center-to- Strand Thickness Cell Voltage Center Center (Perpendicular Mesh Plane Axes Direction Fine Reduction Distance Distance SW/LW Mesh Width) Thickness Area Rs Area Rc Degree F Factor Effect LW [mm] SW [mm] [—] ST [mm] t [mm] [cm²/dm²] [cm²/dm²] [pc/dm²] V [mV] Sample-17 2.94 1.62 0.55 0.58 0.62 8.4 98.0 2102 17 0 Sample-18 5.86 2.66 0.45 1.25 1.01 44.5 61.0 641 17 −21 Sample-19 5.87 3.41 0.58 1.25 1.05 46.6 120.9 499 28 15 Sample-20 2.97 1.53 0.51 0.44 0.19 32.5 44.2 2202 32 26 Sample-21 2.47 2.02 0.82 0.64 0.42 24.6 69.2 2003 34 3 Sample-22 3.79 2.01 0.53 0.75 0.49 44.2 63.6 1311 37 31 Sample-23 3.93 2.05 0.52 0.88 0.46 50.4 71.0 1243 45 29 Sample-24 3.95 1.98 0.50 0.71 0.45 56.6 63.0 1279 46 21 Sample-25 3.94 2.03 0.51 0.69 0.48 52.5 74.0 1252 49 29 Sample-26 3.93 2.05 0.52 0.88 0.46 56.2 69.2 1243 48 26 Sample-27 2.93 1.62 0.55 0.64 0.53 31.0 75.0 2099 49 29 Sample-28 1.95 1.00 0.51 0.21 0.15 27.0 44.7 5132 62 35 Sample-29 2.92 2.00 0.69 0.75 0.60 49.3 77.4 1711 65 28 Sample-30 2.48 1.52 0.61 0.68 0.44 58.6 42.3 2656 66 5 Sample-31 2.93 1.47 0.50 0.54 0.50 35.6 83.4 2325 69 48 Sample-32 3.02 1.24 0.41 0.55 0.45 80.1 38.6 2670 83 59 Sample-33 1.96 1.03 0.53 0.26 0.20 36.5 51.5 4939 93 37 Sample-34 3.04 1.25 0.41 0.55 0.42 78.0 46.5 2638 96 50 Sample-35 2.44 1.20 0.49 0.45 0.49 34.3 84.7 3425 100 42 Sample-36 1.96 1.03 0.53 0.26 0.20 36.5 56.8 4939 102 40 Sample-37 3.04 1.22 0.40 0.48 0.40 76.9 52.1 2696 108 52 Sample-38 3.04 1.22 0.40 0.47 0.37 80.5 56.3 2703 123 52

A correlation of Factor V with the cell voltage of Table 2 is illustrated in FIG. 6. It is found from FIG. 6 that, even in the case of using the expanded metal, the graph becomes a shape approximated to that of FIG. 5 using the punching mesh. Moreover, it is found that, in the case of using the expanded metal, a good cell voltage reduction effect can be obtained when Factor V is 40 or more.

Moreover, even when Factor V is the same value, the cell voltage reduction effect becomes smaller in the case where the SW/LW ratio is more than 0.6 compared to the case where the SW/LW ratio is more than 0.45 and 0.60 or less. On the other hand, it is found that, in the case where the SW/LW ratio is 0.45 or less, the cell voltage reduction effect becomes larger by around 10 mV compared to the case where Factor V is the same value and the SW/LW ratio is more than 0.45 and 0.60 or less. This is a phenomenon which is not found in the punching mesh, and when the expanded metal is used as the electrode shape, the ratio of SW and LW has a greater impact on the cell voltage reduction effect compared to the punching mesh. This is assumed to be caused by the impact of an angle in the thickness direction or the like on current distribution, resistance when generated gas is released from the electrode surface, and the like.

Considering the results of Table 1 and Table 2 as a whole, the structures of Sample-13 in Table 1 and Samples-34, 37, and 38 in Table 2, i.e., the mesh thickness t of from 0.35 to 0.5 mm, the long way center-to-center distance LW of from 2.9 to 3.2 mm, the short way center-to-center distance SW of from 1.1 to 1.4 mm, and the strand (perpendicular mesh width) ST of from 0.4 to 0.7 mm are most preferable.

Therefore, it is found that, according to the present disclosure, an electrolysis electrode having a more preferable shape in electrolyzing pure water, an alkali aqueous solution, or an aqueous solution of an alkali metal chloride at a lower voltage than ever before, and an electrolyzer using the same can be provided.

REFERENCE SIGNS LIST

-   1. Metal perforated plate -   2. One mesh region -   10. Diaphragm electrolyzer -   11. Diaphragm -   12. Anode chamber -   12 a. Anode chamber inlet -   12 b. Anode chamber outlet -   13. Cathode chamber -   13 a. Cathode chamber inlet -   13 b. Cathode chamber outlet -   14. Anode -   15. Cathode -   16. Anode power feeder -   17. Cathode current collector -   18. Gasket 

1.-12. (canceled)
 13. An electrolysis electrode comprising: a metal perforated plate that is an expanded metal and has a value of Factor V of 40 or more, wherein Factor V=Rs×Rc×F/100000, wherein Rs is a planar direction surface area per unit area 1 dm2 (cm2/dm2), wherein Rc is a thickness direction surface area per unit area 1 dm2 [cm2/dm2], wherein F is a number of mesh apertures per unit area 1 dm2 [number/dm2], wherein a ratio of a short way center-to-center distance SW to a long way center-to-center distance LW of a mesh of the expanded metal is 0.45 or less.
 14. The electrolysis electrode of claim 13 wherein the value of Factor V is 70 or more.
 15. The electrolysis electrode of claim 13 wherein the short way center-to-center distance SW of the expanded metal is 2.0 mm or less.
 16. The electrolysis electrode of claim 13 wherein a thickness of the mesh of the expanded metal is 0.5 mm or less.
 17. The electrolysis electrode of claim 13 wherein a thickness of the mesh is from 0.35 to 0.5 mm, wherein the long way center-to-center distance LW of the mesh is from 2.9 to 3.2 mm, wherein the short way center-to-center distance SW of the mesh is from 1.1 to 1.4 mm, wherein a strand ST of the mesh is from 0.4 to 0.7 mm.
 18. An electrolyzer comprising: an anode; and a cathode, wherein at least one of the anode or the cathode is the electrolysis electrode of claim
 13. 19. The electrolyzer of claim 18 comprising a diaphragm for separating an anode chamber and a cathode chamber.
 20. The electrolyzer of claim 19 wherein the diaphragm is an ion exchange membrane.
 21. The electrolyzer of claim 19 wherein the diaphragm is a porous membrane.
 22. The electrolyzer of claim 19 wherein the diaphragm is in contact with the anode.
 23. The electrolyzer of claim 19 wherein the diaphragm is in contact with the cathode. 